Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
2003-02-21
2004-07-06
Prasad, Chandrika (Department: 2839)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C015S210100
Reexamination Certificate
active
06758605
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to cleaning devices intended for optical connectors, and more particularly cleaning devices for the removal of contaminants and small particles from optical fiber and ferrule end faces.
BACKGROUND OF THE INVENTION
Today, optical fiber transmission cables are used for many high rate communication applications. The advantages of using light guiding cables over electrical wires are obvious in terms of frequency bandwidth and data rate. Similarly to standard communication systems, optical fiber networks require amplifying stations for signal boosting over large distances switching, multiplexing, demultiplexing and terminals for fiber test instrumentation and measurements. This implies a lot of optical connectors to be used for connecting the different cables to the communication network.
Optical connectors are opto-mechanical components that allow the light to travel from one fiber to another. Different connector types have been designed for a plurality of applications. For example, FC/PC, ST and SC connector types are used for distinct applications. FC/PC connectors are used for high-end single mode fiber telecommunications systems and ST connectors are for multi-mode fiber applications, such as LAN cabling systems.
The connectors are mechanical male and female plugs composed of ferrules in which the optical fibers are inserted. The plugs are joined together to align the fibers end to end in physical contact in a precise manner. The fiber and ferrule ends are polished to optimize the light transmission. This is to avoid light intensity attenuation at the connector intersection, which would affect the total loss of the signal. Light emitting diodes (LED's) and other optical devices can also be used with some connectors for connection to other devices.
Ferrules are typically made of Zirconia, stainless steel or polyphenylene sulfide.
In practice, the efficiency of the light transmission between the fibers may be affected by dust, dirt and other contaminants. They can interfere with the light signal by producing scattering and absorption sites that may reduce significantly the light transmission. This may also lead to physical damage of the fiber ends and may require the replacement of the connector. Another potential hazard is abrasive contaminant particles that may damage the fiber end surface, especially if the ferrules are rotated against each other during the initial mating.
In order to avoid transmission problems and keep the ferrules and fiber ends in good conditions, connector cleaning must be done frequently. Several methods are used to clean the optical fiber end surfaces before mating connectors.
The first method involves the use of compressed air sprayed across the ferrule to remove contaminants from the fiber surface. The drawback of this method is that the force applied is not always sufficient to be effective. Moreover, the compressed air itself may also contaminate the surface with small particles.
Other methods use wet and/or dry cleaning. Wet cleaning utilizes isopropyl alcohol and lint-free cloths for wiping across the ferrule end face to remove the contaminants. The problem is that lint-free cloth can still leave contaminant materials on the surface. The wiping action may also scratch the surface if abrasive contaminants are present.
The dry cleaning approach involves a special textile cleaning tape or film on a reel inside a cartridge. The cartridge stores the tape reel and provides a window onto a short portion of the cloth tape for cleaning the ferrule ends of connectors. Like the wet cleaning approach, contaminants may still stay on the surface. The sliding and wiping action of the film with abrasive particles may damage the surface, depending on the manual pressure applied. The cleaning quality is also very dependent on the operator skill.
Other methods use cleaners having a housing with a nose that can be mated to an optical connector. A cleaning tape, such as a tape fabricated of a woven fabric, cleans the ferrule and the optical fiber ends. A supply reel is mounted in the housing for supplying the cleaning tape. The whole reel and fabric mechanism is rotated together against the ferrule with a fixed pressure. The disadvantages of such a system are that the device does not allow control of the applied pressure on the ferrule and that the portion of the fabric used is manually controlled. The device cannot automatically manage the fabric length used for the cleaning process. Moreover, the device has a lot of moving mechanical parts, which can be troublesome and could create instabilities and uncertainties during the cleaning process.
An example of a prior art cleaner for the end face of a ferrule of a connector is Japanese published patent application no. 2002-90576. It describes a pin projecting from a rotary part which is rotated in the axial direction. The pin is provided with a groove, along the side face of which a thread for cleaning the ferrule is stretched and wound at a prescribed speed. As a result, by pressing the pin on the ferrule, a new part of the thread constantly comes into contact with the ferrule to enable its tip end face, particularly its center part, to be cleaned. The thread therefore cleans the end face of the ferrule as the pin rotates 360°. The grooves allow the thread to be directed properly and to be in constant contact with the ferrule end face.
Some problems identified with the prior art device of Japanese published patent application no. 2002-90576 are that the thread may become dirty prior to reaching the ferrule as it accumulates contaminants while circulating in the groove. The thread may also become loose as it is circulated in the device. Finally, the pin of the prior art devices may damage the end face of the ferrule as pressure is exerted by the device to activate the cleaning mechanism.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to solve, separately or in combination, the above mentioned problems, namely ensuring the cleanliness of the fabric used to clean the ferrule and protecting the ferrule end face by preventing too much pressure from being applied on the ferrule end face.
A method and device for cleaning at least an end face of an optical device retained within an optical connector using a cleaning fabric, comprises, alone or in combination, a) preventing the cleaning fabric from contacting the connector prior to contacting the end face of the optical device; b) a cleaning nose being made of a nose material having a hardness less than that of a material of the optical device with a flexural modulus greater than 2700 MPa and c) ensuring a constant tension on the fabric as it is circulated.
According to a first broad aspect of the present invention, there is provided a device for cleaning at least an end face of an optical device retained within an optical connector using a cleaning fabric, comprising: a housing having a handle portion, a supply for the cleaning fabric and a forward tip, the forward tip being adapted to mate with the optical connector; a cleaning nose within the forward tip adapted to receive the cleaning fabric and to be at least partially inserted in the optical connector to contact at least the end face of the optical device; circulation means for circulating the cleaning fabric within the housing and on the cleaning nose to expose an unused portion of cleaning fabric on an extremity of the cleaning nose contacting the end face; the cleaning nose having a supply channel and a take-up groove located diametrically opposed on the extremity of the nose, the channel and the groove being adapted to respectively receive a supply of the fabric and a contaminated portion of the fabric, the fabric being contaminated on contact with the end face on the extremity; the supply channel preventing the fabric from being contaminated by the optical connector prior to contacting the end face of the optical device.
According to another aspect of the present invention, there is provided a device for cleaning at least an end face of a
Brault Louis
Giroux Jean
Villemaire André
Chabot Isabelle
Prasad Chandrika
Renault Ogilvy
Telops Inc.
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